NBDE Part 1 is NOT the same as the USMLE Step1/CBSE. The material is completely different with almost no overlap. Using NBDE Part 1 as a study for the CBSE will NOT work. If you are preparing for the CBSE to apply for OMFS residency, you must use USMLE Step1-specific review materials (i.e. UWorld Qbank, Kaplan Qbank, and First Aid for USMLE Step1). Take this exam seriously as it is an absolute beast - See the other posts about CBSE prep - there are about 20 on SDN (mostly in the residency pages)